Download Chapter 4 Section 2 Notes - Overview of Photosynthesis

Chapter 4 Section 2 Notes - Overview of Photosynthesis




Plants are producers – they produce their own source of energy.
Photosynthesis – the process by which light energy is converted to
chemical energy; produces sugar and oxygen from carbon dioxide and
water – takes place in chloroplasts
Chlorophyll – molecule in chloroplasts that absorbs some of the energy
in visible light (made of different wavelengths or colors of light)
Plants use energy in visible light for photosynthesis
* 2 Main parts of chloroplasts are needed for photosynthesis:
1. grana (granum, singular) – stacks of compartments called thylakoids –
shaped like coins, flat and circular and they are enclosed by membranes that
contain chlorophyll
2. stroma – fluid that is all around the grana inside the chloroplast
 2 stages of photosynthesis:
1. Light-dependent reactions – capture energy from sunlight
 takes place in the thylakoids and their membranes
- chlorophyll absorbs energy from sunlight, energy moves along the
thylakoid membrane and is transferred to molecules that carry
energy, such as ATP
- during this process H2O molecules are broken down and O2
molecules are released
2. Light-independent reactions – use the energy from the lightdependent reactions to make sugars (Calvin Cycle)
 takes place in the stroma
- CO2 and energy from the light-dependent reactions are used to
build sugars, usually glucose (C6H12O6)
6CO2 + 6H2O + light energy ----- C6H12O6 + 6O2
Carbon + water + light energy ------ a sugar + oxygen
Dioxide
* Plants often use the simple sugars produced by photosynthesis to build starch
and cellulose molecules.